Study the immune response to tumor associated antigens of virus induced tumors in experimental animals with particular attention to the mechanisms involved. The following specific areas will be included: kinetics and specificity of in vitro cell-mediated immune response to murine sarcoma virus and to murine leukemia viruses with attention not only to direct cytotoxicity but to inhibition of this activity by specific antigens in an assay developed in this laboratory; cryopreservation of cells active in the immune response; lymphocyte stimulation and the in vitro generation of cytotoxic cells as well as mitogen induced activity and the adoptive transfer of such generated activity; inhibition of immune responses by tumor cells and suppressor cells and the further evaluation of natural immunity as measured by in vitro assays and adoptive transfer. Further attempts to isolate and purify tumor associated antigens and measure their activity in vitro and in vivo will be made. Continued efforts to study the immune response in human tumor systems with the use of leukocyte migration inhibition, rosette formation, lymphocyte stimulation and delayed hypersensitivity testing will be made. Tumor associated antigens will be isolated from fresh and tissue cultured tumor cells and tested for biologic activity.